Struct HashSet

pub struct HashSet<A, S = RandomState> { /* private fields */ }

An unordered set.

An immutable hash set using [hash array mapped tries] 1.

Most operations on this set are O(log_x n) for a suitably high x that it should be nearly O(1) for most sets. Because of this, it’s a great choice for a generic set as long as you don’t mind that values will need to implement Hash and Eq.

Values will have a predictable order based on the hasher being used. Unless otherwise specified, this will be the standard RandomState hasher.

Implementations

impl<A> HashSet<A, RandomState>

pub fn new() -> Self

Construct an empty set.

impl<A> HashSet<A, RandomState>

where A: Hash + Eq + Clone,

pub fn unit(a: A) -> Self

Construct a set with a single value.

Examples

let set = HashSet::unit(123);
assert!(set.contains(&123));

impl<A, S> HashSet<A, S>

pub fn is_empty(&self) -> bool

Test whether a set is empty.

Time: O(1)

Examples

assert!(
  !hashset![1, 2, 3].is_empty()
);
assert!(
  HashSet::<i32>::new().is_empty()
);

pub fn len(&self) -> usize

Get the size of a set.

Time: O(1)

Examples

assert_eq!(3, hashset![1, 2, 3].len());

pub fn ptr_eq(&self, other: &Self) -> bool

Test whether two sets refer to the same content in memory.

This is true if the two sides are references to the same set, or if the two sets refer to the same root node.

This would return true if you’re comparing a set to itself, or if you’re comparing a set to a fresh clone of itself.

Time: O(1)

pub fn with_hasher<RS>(hasher: RS) -> Self

where Arc<S>: From<RS>,

Construct an empty hash set using the provided hasher.

pub fn hasher(&self) -> &Arc<S>

Get a reference to the set’s BuildHasher.

pub fn new_from<A1>(&self) -> HashSet<A1, S>

where A1: Hash + Eq + Clone,

Construct an empty hash set using the same hasher as the current hash set.

pub fn clear(&mut self)

Discard all elements from the set.

This leaves you with an empty set, and all elements that were previously inside it are dropped.

Time: O(n)

Examples

let mut set = hashset![1, 2, 3];
set.clear();
assert!(set.is_empty());

pub fn iter(&self) -> Iter<'_, A>

Get an iterator over the values in a hash set.

Please note that the order is consistent between sets using the same hasher, but no other ordering guarantee is offered. Items will not come out in insertion order or sort order. They will, however, come out in the same order every time for the same set.

impl<A, S> HashSet<A, S>

where A: Hash + Eq, S: BuildHasher,

pub fn contains<BA>(&self, a: &BA) -> bool

where BA: Hash + Eq + ?Sized, A: Borrow<BA>,

Test if a value is part of a set.

Time: O(log n)

pub fn is_subset<RS>(&self, other: RS) -> bool

where RS: Borrow<Self>,

Test whether a set is a subset of another set, meaning that all values in our set must also be in the other set.

Time: O(n log n)

pub fn is_proper_subset<RS>(&self, other: RS) -> bool

where RS: Borrow<Self>,

Test whether a set is a proper subset of another set, meaning that all values in our set must also be in the other set. A proper subset must also be smaller than the other set.

Time: O(n log n)

impl<A, S> HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

pub fn insert(&mut self, a: A) -> Option<A>

Insert a value into a set.

Time: O(log n)

pub fn remove<BA>(&mut self, a: &BA) -> Option<A>

where BA: Hash + Eq + ?Sized, A: Borrow<BA>,

Remove a value from a set if it exists.

Time: O(log n)

pub fn update(&self, a: A) -> Self

Construct a new set from the current set with the given value added.

Time: O(log n)

Examples

let set = hashset![123];
assert_eq!(
  set.update(456),
  hashset![123, 456]
);

pub fn without<BA>(&self, a: &BA) -> Self

where BA: Hash + Eq + ?Sized, A: Borrow<BA>,

Construct a new set with the given value removed if it’s in the set.

Time: O(log n)

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&A) -> bool,

Filter out values from a set which don’t satisfy a predicate.

This is slightly more efficient than filtering using an iterator, in that it doesn’t need to rehash the retained values, but it still needs to reconstruct the entire tree structure of the set.

Time: O(n log n)

Examples

let mut set = hashset![1, 2, 3];
set.retain(|v| *v > 1);
let expected = hashset![2, 3];
assert_eq!(expected, set);

pub fn union(self, other: Self) -> Self

Construct the union of two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{1, 2, 3};
assert_eq!(expected, set1.union(set2));

pub fn unions<I>(i: I) -> Self

where I: IntoIterator<Item = Self>, S: Default,

Construct the union of multiple sets.

Time: O(n log n)

pub fn difference(self, other: Self) -> Self

👎Deprecated since 2.0.1: to avoid conflicting behaviors between std and imbl, the difference alias for symmetric_difference will be removed.

Construct the symmetric difference between two sets.

This is an alias for the symmetric_difference method.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{1, 3};
assert_eq!(expected, set1.difference(set2));

pub fn symmetric_difference(self, other: Self) -> Self

Construct the symmetric difference between two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{1, 3};
assert_eq!(expected, set1.symmetric_difference(set2));

pub fn relative_complement(self, other: Self) -> Self

Construct the relative complement between two sets, that is the set of values in self that do not occur in other.

Time: O(m log n) where m is the size of the other set

Examples

let set1 = ordset!{1, 2};
let set2 = ordset!{2, 3};
let expected = ordset!{1};
assert_eq!(expected, set1.relative_complement(set2));

pub fn intersection(self, other: Self) -> Self

Construct the intersection of two sets.

Time: O(n log n)

Examples

let set1 = hashset!{1, 2};
let set2 = hashset!{2, 3};
let expected = hashset!{2};
assert_eq!(expected, set1.intersection(set2));

Trait Implementations

impl<'a, A, S> Add for &'a HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

type Output = HashSet<A, S>

The resulting type after applying the + operator.

fn add(self, other: Self) -> Self::Output

Performs the + operation.

impl<A, S> Add for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

type Output = HashSet<A, S>

The resulting type after applying the + operator.

fn add(self, other: Self) -> Self::Output

Performs the + operation.

impl<A, S> Clone for HashSet<A, S>

where A: Clone,

fn clone(&self) -> Self

Clone a set.

Time: O(1)

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<A, S> Debug for HashSet<A, S>

where A: Hash + Eq + Debug, S: BuildHasher,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<A, S> Default for HashSet<A, S>

where S: BuildHasher + Default,

fn default() -> Self

Returns the “default value” for a type.

impl<'de, A: Deserialize<'de> + Hash + Eq + Clone, S: BuildHasher + Default> Deserialize<'de> for HashSet<A, S>

fn deserialize<D>(des: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<A, S, R> Extend<R> for HashSet<A, S>

where A: Hash + Eq + Clone + From<R>, S: BuildHasher,

fn extend<I>(&mut self, iter: I)

where I: IntoIterator<Item = R>,

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl<'a, A, S> From<&'a [A]> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(slice: &'a [A]) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a BTreeSet<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(btree_set: &BTreeSet<A>) -> Self

Converts to this type from the input type.

impl<'s, 'a, A, OA, SA, SB> From<&'s HashSet<&'a A, SA>> for HashSet<OA, SB>

where A: ToOwned<Owned = OA> + Hash + Eq + ?Sized, OA: Borrow<A> + Hash + Eq + Clone, SA: BuildHasher, SB: BuildHasher + Default,

fn from(set: &HashSet<&A, SA>) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a HashSet<A>> for HashSet<A, S>

where A: Eq + Hash + Clone, S: BuildHasher + Default,

fn from(hash_set: &HashSet<A>) -> Self

Converts to this type from the input type.

impl<'a, A: Hash + Eq + Ord + Clone, S: BuildHasher> From<&'a HashSet<A, S>> for OrdSet<A>

fn from(hashset: &HashSet<A, S>) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a OrdSet<A>> for HashSet<A, S>

where A: Ord + Hash + Eq + Clone, S: BuildHasher + Default,

fn from(ordset: &OrdSet<A>) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a Vec<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vec: &Vec<A>) -> Self

Converts to this type from the input type.

impl<'a, A, S> From<&'a Vector<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vector: &Vector<A>) -> Self

Converts to this type from the input type.

impl<A, S, const N: usize> From<[A; N]> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(arr: [A; N]) -> Self

Converts to this type from the input type.

impl<A, S> From<HashSet<A>> for HashSet<A, S>

where A: Eq + Hash + Clone, S: BuildHasher + Default,

fn from(hash_set: HashSet<A>) -> Self

Converts to this type from the input type.

impl<A: Hash + Eq + Ord + Clone, S: BuildHasher> From<HashSet<A, S>> for OrdSet<A>

fn from(hashset: HashSet<A, S>) -> Self

Converts to this type from the input type.

impl<A, S> From<OrdSet<A>> for HashSet<A, S>

where A: Ord + Hash + Eq + Clone, S: BuildHasher + Default,

fn from(ordset: OrdSet<A>) -> Self

Converts to this type from the input type.

impl<A, S> From<Vec<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vec: Vec<A>) -> Self

Converts to this type from the input type.

impl<A, S> From<Vector<A>> for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn from(vector: Vector<A>) -> Self

Converts to this type from the input type.

impl<A, RA, S> FromIterator<RA> for HashSet<A, S>

where A: Hash + Eq + Clone + From<RA>, S: BuildHasher + Default,

fn from_iter<T>(i: T) -> Self

where T: IntoIterator<Item = RA>,

Creates a value from an iterator.

impl<'a, A, S> IntoIterator for &'a HashSet<A, S>

where A: Hash + Eq, S: BuildHasher,

type Item = &'a A

The type of the elements being iterated over.

type IntoIter = Iter<'a, A>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<A, S> IntoIterator for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

type Item = A

The type of the elements being iterated over.

type IntoIter = ConsumingIter<<HashSet<A, S> as IntoIterator>::Item>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a, A, S> Mul for &'a HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

type Output = HashSet<A, S>

The resulting type after applying the * operator.

fn mul(self, other: Self) -> Self::Output

Performs the * operation.

impl<A, S> Mul for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher,

type Output = HashSet<A, S>

The resulting type after applying the * operator.

fn mul(self, other: Self) -> Self::Output

Performs the * operation.

impl<A, S> PartialEq for HashSet<A, S>

where A: Hash + Eq, S: BuildHasher + Default,

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<A: Serialize + Hash + Eq, S: BuildHasher + Default> Serialize for HashSet<A, S>

fn serialize<Ser>(&self, ser: Ser) -> Result<Ser::Ok, Ser::Error>

where Ser: Serializer,

Serialize this value into the given Serde serializer.

impl<A, S> Sum for HashSet<A, S>

where A: Hash + Eq + Clone, S: BuildHasher + Default,

fn sum<I>(it: I) -> Self

where I: Iterator<Item = Self>,

Takes an iterator and generates Self from the elements by “summing up” the items.

impl<A, S> Eq for HashSet<A, S>

where A: Hash + Eq, S: BuildHasher + Default,